In a liquid chromatograph, a sample is injected into a column, and components of the sample are temporally separated using a difference in the affinity and a distribution state of the components of the sample to two phases of a stationary phase and a mobile phase. Each component is eluted from the column, then passes through a pipe together with the mobile phase, and is introduced into a detector to be subjected to an analysis.
Various methods are applied to the detector. At present, especially optical detectors such as an absorbance detector and a fluorescence detector are most frequently applied for reasons of a wide application range thereof and the like.
Light absorption characteristics and the like of a sample component are susceptible to temperature. Hence, if the temperature of the mobile phase containing the sample component changes, the output of the detector is influenced by the change in temperature, so that correct analysis results cannot be obtained. In the case where the mobile phase is influenced by a temperature fluctuation in a relatively long cycle, the influence appears as a change in baseline of the detector output. In the case where the mobile phase is influenced by a temperature fluctuation in a cycle shorter than a change in baseline, the influence appears as noise. In order to avoid such influences, the temperature of the sample component (that is, the temperature of the mobile phase) at the time of detection by the detector needs to be kept constant.
Hence, temperature control of constituent parts of the liquid chromatograph from the column to the detector is important. In the liquid chromatograph, normally, the column and the detector are each modularized, modules suited to an analysis purpose are selected and combined, and the modules are connected by a pipe, whereby desired performance is obtained. The temperatures of the modularized column and the modularized detector are controlled independently of each other.
For example, JP-A 2010-48554 discloses a technique of controlling the temperature of a column. According to this technique, the column is housed inside of a constant temperature bath, and a temperature sensor is attached to the outer surface of the column. Electric current supplied to a heater provided in the constant temperature bath is controlled such that a value of the temperature sensor is a target temperature, whereby the temperature of the column (that is, the temperature of a mobile phase) is controlled.
Further, JP-A 2008-256530 discloses a technique of controlling the temperature of a detector. According to this technique, a flow cell is irradiated with light emitted from a light source, and the amount of transmitted light is detected by a photodetector. This configuration includes: a sample temperature regulation block for housing the flow cell therein; and a photodetector temperature regulation block for housing the photodetector therein, and also includes a simultaneous temperature regulation block in contact with the two blocks. Then, the simultaneous temperature regulation block is regulated to a constant temperature, whereby the temperature of a mobile phase supplied to the flow cell and the temperature of the photodetector are kept constant.
As described above, a pipe is necessary to send a mobile phase containing a sample from a column module to a detector module, and the temperature of the mobile phase fluctuates under influences of surrounding environments also when the mobile phase passes through the pipe between the column module and the detector module. In view of the above, conventionally, as shown in FIG. 4, a pipe winding unit 42 is provided in the detector module separately from a pipe 41, and the pipe winding unit 42 is placed in close contact around a temperature regulation block. A region sandwiched between two double wavy lines in FIG. 4 shows the inside of a temperature regulation block 46, where a light source 45, a flow cell 43, and a photodetector 44 are provided.
In this configuration, even if the temperature of the mobile phase is changed by influences of surrounding environments when the mobile phase passes through the pipe 41 between a column module 47 and a detector module 40, the temperature of the mobile phase is made constant by heat exchange with the temperature regulation block and the like when the mobile phase passes through the pipe winding unit 42. Accordingly, the temperature of the mobile phase supplied to the flow cell 43 is always constant, and the output of the photodetector 44 can be prevented from being influenced.